DOCSLIB.ORG

Triaxial Shear Test

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Triaxial Shear Test TRIAXIAL SHEAR TEST 1. Objective The tri-axial shear test is most versatile of all the shear test testing methods for getting shear strength of soil i.e. Cohesion (C) and Angle of Internal Friction (Ø), though it is bit complicated. This test can measure the total as well as effective stress parameters both. These two parameters are required for design of slopes, calculation of bearing capacity of any strata, calculation of consolidation parameters and in many other analyses. This test can be conducted on any type of soil, drainage conditions can be controlled, pore water pressure measurements can be made accurately and volume changes can be measured. In this test, the failure plane is not forced, the stress distribution of failure plane is fairly uniform and specimen can fail on any weak plane or can simply bulge. 2. Apparatus Required Fig. 1: Triaxial Shear Test Apparatus Fig. 2: Triaxial Shear Test Setup Fig. 3: 3.8 cm (1.5 inch) internal diameter 12.5 cm (5 inches) long sample tubes. Fig. 4: Rubber Ring Fig. 5: Open ended cylindrical section Fig. 6: Weighing balance 3. Reference 1. IS 2720(Part 11):1993 Determination of the shear strength parameters of a specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure (first revision). Reaffirmed- Dec 2016. 2. IS 2720(Part 12):1981 Determination of Shear Strength parameters of Soil from consolidated undrained triaxial compression test with measurement of pore water pressure (first revision). Reaffirmed- Dec 2016. 4. Procedure 4.1 Triaxial Test on Cohesive Soil: 4.1.1 Consolidated Undrained test: A de-aired, coarse porous disc or stone is placed on the top of the pedestal in the triaxial test apparatus. A filter paper disc is kept over the porous stone. The specimen of the cohesive soil is then placed over the filter paper disc. The usual size of the specimen is about 37.5mm diameter and 75.0mm height. A porous stone is also placed on the top of the specimen. De-aired vertical filter strips are placed at regular spacing around the entire periphery such that these touch both the porous stones. The sample in then enclosed in a rubber membrane, which is slided over the specimen with the help of a membrane stretcher. The membrane is sealed to the specimen with O-rings. The triaxial cell is placed over the base and fixed to it by tightening the nuts. The cell is then filled with water by connecting it to the pressure supply. Some space in the top portion of the cell is filled by injecting oil through the oil valve. When excess oil begins to spill out through the air-vent valve, both the valves (oil valve and air-vent valve) are closed. Pressure is applied to the water fiiled in the cell by connecting it to the mercury-pot system. As soon as the pressure acts on the specimen, it starts consolidating. The specimen is connected to the burette through pressure connections for measurement of volume changes. The consolidation is complete when there is no more volume change. When the consolidation is complete, the specimen is ready for being sheared. The drainage valve is closed. The pore water pressure measurement device is attached to the specimen through the pressure connections. The proving ring dial gauge is set to zero. Using the manual control provided in the loading frame, the ram is pushed into the cell but not allowed to touch the loading cap. The loading machine is then run at the selected speed. The proving ring records the force due to friction and the upward thrust acting on the ram. The machine is stopped, and with the manual control, the ram is pushed further into the cell bringing it in contact with the loading cap. The dial gauge for the measuring axial deformation of the specimen is set to zero. The sample is sheared by applying the deviator stress by the loading machine. The proving ring readings are generally taken corresponding to axial strains of 1/3%, 2/3%, 1%, 2%, 3%, 4%, 5%, until failure or 20% axial strain. Upon completion of the test, the loading is shut off. Using the manual control, all additional axial stress is removed. The cell pressure is then reduced to zero and the cell is emptied. The triaxial cell is unscrewed and removed from the base. O-rings are taken out, and the membrane is removed. The specimen is then recovered after removing the loading cap and the top porous stone. The filter paper strips are peeled off. The post-shear mass and length are determined. The water content of the specimen is also found. 4.1.2 Unconsolidated Undrained test: The procedure is similar to that for a consolidated-undrained test, with one basic difference that the specimen is not allowed to consolidate in the first stage. The drainage valve during the test is kept closed. However, the specimen can be connected to the pore-water pressure measurement device if required. Shearing of the specimen is started just after the application of the cell pressure. The second stage is exactly the same as in the consolidated-undrained test described above. 4.1.3 Consolidated Drained test: The procedure is similar to that for a consolidated-undrained test, with one basic difference that the specimen is sheared slowly in the second stage. After the consolidation of the specimen in the first stage, the drainage valve is not closed. It remains connected to the burette throughout the test. The volume changes during the shearing stage are measured with the help of the burette. As the permeability of cohesive soils is very low, it takes 4-5 days for the consolidated drained test. 4.2. Triaxial tests on Cohesionless Soils: Triaxial tests on specimens of cohesionless soils can be conducted using the procedure as described for cohesive soils. As the samples of cohesionless soils cannot stand of their own, a special procedure is used for preparation of the sample as described below. A metal former, which is a split mould of about 38.5mm internal diameter, is used for the preparation of the sample (Fig.3). A coarse porous stone is placed on the top of the pedestal of the triaxial base and the pressure connection is attached to a burette (not shown). One end of a membrane is sealed to the pedestal by O-rings. The metal former is clamped to the base. The upper metal ring of the former is kept inside the top end of the rubber membrane and is held with the help of clamp before placing the funnel and the rubber bung in position . The membrane and the funnel are filled with de-aired water. The cohesionless soil which is to be tested is saturated by mixing it with enough water in a beaker. The mixture is boiled to remove the entrapped air. The saturated soil is deposited in the funnel, with a stopper in position, in the required quantity. The glass rod is then removed and the sample builds up by a continuous rapid flow of saturated soil in the former. The funnel is then removed. The funnel is then removed. The sample may be compacted if required. The surface of the sample is leveled and a porous stone is placed on its top. The loading cap is placed gently on the top porous stone. O-rings are fixed over the top of the rubber membrane. A small negative pressure is applied to the sample by lowering the burette. The negative pressure gives rigidity to the sample and it can stand without any lateral support. For sample of 37.5mm diameter, a negative pressure of 20cm of water (or 2 kN/m2) is sufficient. As soon as the negative pressure is applied, the consolidation of the sample occurs and it slightly shortens. The diameter of the upper porous stone should be slightly smaller than that of the specimen so that it can go inside when the sample shortens; otherwise, a neck is formed. The split mould is then removed and the diameter and the height of the sample are measured. The thickness of the membrane is deducted from the total diameter to get the net diameter of the sample. The cell is then placed over the base and clamped to the base. It is then filled with water. The rest of the procedure is the same as for cohesive soils. 5. Computation Of Various Parameters: 5.1 Post-Consolidation Dimensions: In consolidated-drained and consolidated-undrained tests, the consolidation of the specimen takes place during the first stage. As the volume of the specimen decreases, its post-consolidation dimensions are different from the initial dimensions. The post consolidation dimensions can be determined approximately assuming that the sample remains cylindrical and it behaves isotropically. Let Li, Di and Vi be the length, diameter and the volume of the specimen before consolidation. Let L0, D0 and V0 be the corresponding quantities after consolidation. Volumetric change, Δ Vi = Vi – V0 Volumetric change is measured with the help of burette. Volumetric strain, Єv = Δ Vi / Vi For isotropic consolidation, the volumetric strain is three times the linear strain (Єl), thus: Єl = Єv / 3 L0 = Li – Δ Li = Li – Li x Єl L0 = Li (1 - Єl) = Li (1 – Єv/3) Similarly, D0 = Di (1 – Єv/3) The post consolidation diameter D0 can also be computed after L0 has been determined from the relation: (ϖ/4. D 02) x L0 = V0 Or D0 = √ V0 / [(ϖ/4) x L0] 5.2 Cross-sectional area during Shear Stage: As the sample is sheared, its length decreases and the diameter increases.
Load more

Recommended publications
  • SHEAR Axial and Direct Shear Module for GEOSYSTEM® for Windows
    GEOSYSTEM® SHEAR Axial and Direct Shear Module for GEOSYSTEM® for Windows Copyright © 2004 Von Gunten Engineering Software, Inc. 363 West Drake #10 Fort Collins, CO 80526 www.geosystemsoftware.com Information in this document is subject to change without notice and does not represent a commitment on the part of Von Gunten Engineering Software, Inc. The software described in this document is furnished under a license agreement, and the software may be used or copied only in accordance with the terms of that agreement. The licensee may make copies of the software for backup purposes only. No part of this manual may be reproduced in any form for purposes other than the licensee’s personal use without the written consent of Von Gunten Engineering Software, Inc. Copyright © Von Gunten Engineering Software, Inc. 2004. All rights reserved. Published in the United States of America. GEOSYSTEM® is a registered trademark of VES, Inc. Windows® is a registered trademark of Microsoft Corporation Terms of License Agreement 1. The Licensee agrees not to sell or otherwise distribute the program or the program documentation. Each copy of the program is licensed only for use at a single address. 2. The Licensee agrees not to hold Von Gunten Engineering Software, Inc. (VES, Inc.) liable for any harm, damages claims, losses or expenses arising out of any act or occurrence related in any way to the use of the program. 3. The program is warranted to fully perform the tasks described in the program documentation. All results of the operation of the program are subject to the further engineering judgment, prudence, and study of the user.
    [Show full text]
  • An Empirical Approach for Tunnel Support Design Through Q and Rmi Systems in Fractured Rock Mass
    applied sciences Article An Empirical Approach for Tunnel Support Design through Q and RMi Systems in Fractured Rock Mass Jaekook Lee 1, Hafeezur Rehman 1,2, Abdul Muntaqim Naji 1,3, Jung-Joo Kim 4 and Han-Kyu Yoo 1,* 1 Department of Civil and Environmental Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan 426-791, Korea; [email protected] (J.L.); [email protected] (H.R.); [email protected] (A.M.N.) 2 Department of Mining Engineering, Faculty of Engineering, Baluchistan University of Information Technology, Engineering and Management Sciences (BUITEMS), Quetta 87300, Pakistan 3 Department of Geological Engineering, Faculty of Engineering, Baluchistan University of Information Technology, Engineering and Management Sciences (BUITEMS), Quetta 87300, Pakistan 4 Korea Railroad Research Institute, 176 Cheoldobangmulgwan-ro, Uiwang-si, Gyeonggi-do 16105, Korea; [email protected] * Correspondence: [email protected]; Tel.: +82-31-400-5147; Fax: +82-31-409-4104 Received: 26 November 2018; Accepted: 14 December 2018; Published: 18 December 2018 Abstract: Empirical systems for the classification of rock mass are used primarily for preliminary support design in tunneling. When applying the existing acceptable international systems for tunnel preliminary supports in high-stress environments, the tunneling quality index (Q) and the rock mass index (RMi) systems that are preferred over geomechanical classification due to the stress characterization parameters that are incorporated into the two systems. However, these two systems are not appropriate when applied in a location where the rock is jointed and experiencing high stresses. This paper empirically extends the application of the two systems to tunnel support design in excavations in such locations.
    [Show full text]
  • Multidisciplinary Design Project Engineering Dictionary Version 0.0.2
    Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions.
    [Show full text]
  • A. Refereed Archival Publications
    A. Refereed Archival Publications J. Casey and P.M. Naghdi, "A Remark on the Use of the Decomposition F = FeFpin Plasticity," Al. Journal of Applied Mechanics, 47 (1980) 672-675. A. Seidenberg and J. Casey, "The Ritual Origin of the Balance," Archive for History of Exact A2. Sciences, 23 (1980) 179-226. J. Casey and P.M. Naghdi, "An Invariant Infinitesimal Theory of Motions Superposed on a A3. Given Motion," Archive for Rational Mechanics and Analysis, 76(1981) 355-391. J. Casey and P.M. Naghdi, "On the Characterization of Strain-Hardening in Plasticity," Journal A4. of Applied Mechanics, 48 (1981) 285-296. J. Casey, "Small Deformations Superposed on Large Deformations in a General Elastic-Plastic A5. Material," International Journal of Solids and Structures, 19 (1983) 1115-1146. J. Casey and P.M. Naghdi, "A Remark on the Definition of Hardening, Softening and Perfectly A6. Plastic Behavior, Acta Mechanica, 48 (1983) 91-94. J. Casey and P.M. Naghdi, "On the Nonequivalence of the Stress-Space and Strain Space A7. Formulations of Plasticity," Journal of Applied Mechanics, 50 (1983) 350-354. J. Casey, "A Treatment of Rigid Body Dynamics," Journal of Applied Mechanics,50 (1983) 905- A8. 907 and 51 (1984) 227. J. Casey and H.H. Lin, "Strain-Hardening Topography of Elastic-Plastic Materials, Journal of A9. Applied Mechanics, 50 (1983) 795-801. J. Casey and P.M. Naghdi, "On the Use of Invariance Requirements for the Intermediate A10. Configurations Associated with the Polar Decomposition of a Deformation Gradient," Quarterly of Applied Mathematics, 41 (1983) 339-342. J. Casey and P.M.
    [Show full text]
  • FHWA/TX-07/0-5202-1 Accession No
    Technical Report Documentation Page 1. Report No. 2. Government 3. Recipient’s Catalog No. FHWA/TX-07/0-5202-1 Accession No. 4. Title and Subtitle 5. Report Date Determination of Field Suction Values, Hydraulic Properties, August 2005; Revised March 2007 and Shear Strength in High PI Clays 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Jorge G. Zornberg, Jeffrey Kuhn, and Stephen Wright 0-5202-1 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Center for Transportation Research 11. Contract or Grant No. The University of Texas at Austin 0-5202 3208 Red River, Suite 200 Austin, TX 78705-2650 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Texas Department of Transportation Technical Report Research and Technology Implementation Office September 2004–August 2006 P.O. Box 5080 14. Sponsoring Agency Code Austin, TX 78763-5080 15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. Project Title: Determination of Field Suction Values in High PI Clays for Various Surface Conditions and Drain Installations 16. Abstract Moisture infiltration into highway embankments constructed by the Texas Department of Transportation (TxDOT) using high Plasticity Index (PI) clays results in changes in shear strength and in flow pattern that leads to recurrent slope failures. In addition, soil cracking over time increases the rate of moisture infiltration. The overall objective of this research is to determine the suction, hydraulic properties, and shear strength of high PI Texas clays. Specifically, two comprehensive experimental programs involving the characterization of unsaturated properties and the shear strength of a high PI clay (Eagle Ford clay) were conducted.
    [Show full text]
  • Evaluation of Soil Dilatancy
    The Influence of Grain Shape on Dilatancy Item Type text; Electronic Dissertation Authors Cox, Melissa Reiko Brooke Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 24/09/2021 03:25:54 Link to Item http://hdl.handle.net/10150/195563 THE INFLUENCE OF GRAIN SHAPE ON DILATANCY by MELISSA REIKO BROOKE COX ________________________ A Dissertation Submitted to the Faculty of the DEPARTMENT OF CIVIL ENGINEERING AND ENGINEERING MECHANICS In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY WITH A MAJOR IN CIVIL ENGINEERING In the Graduate College THE UNIVERISTY OF ARIZONA 2 0 0 8 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Melissa Reiko Brooke Cox entitled The Influence of Grain Shape on Dilatancy and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy ___________________________________________________________________________ Date: October 17, 2008 Muniram Budhu ___________________________________________________________________________ Date: October 17, 2008 Achintya Haldar ___________________________________________________________________________ Date: October 17, 2008 Chandrakant S. Desai ___________________________________________________________________________ Date: October 17, 2008 John M. Kemeny Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.
    [Show full text]
  • The Influence of Slenderness Ratios on Triaxial Shear Testing
    Proceedings of the Iowa Academy of Science Volume 73 Annual Issue Article 41 1966 The Influence of Slenderness Ratios on riaxialT Shear Testing Eugene R. Moores Sunray D-X Oil Company J. M. Hoover Iowa State University Let us know how access to this document benefits ouy Copyright ©1966 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Moores, Eugene R. and Hoover, J. M. (1966) "The Influence of Slenderness Ratios on riaxialT Shear Testing," Proceedings of the Iowa Academy of Science, 73(1), 285-292. Available at: https://scholarworks.uni.edu/pias/vol73/iss1/41 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. Moores and Hoover: The Influence of Slenderness Ratios on Triaxial Shear Testing The Influence of Slende,rness Ratios on Triaxial Sihear Testing 1 EUGENE R. MooRES AND J. M. Hoovm2 Abstract. Determination of the effect of the slenderness ratio on the results of the triaxial test depends, theoretically, on the boundary conditions induced by ( a) shape of the test specimen, ( o) manner of the transmission of the external load, and · ( c) deformations. From a practical point of view enough length should be available to develop two complete cones of failure and the length of the specimen should equal the diameter times the 0 tangent of (45 + .p/2) • Most workers in the field of triaxial testing of soils accept a slenderness ratio of from 1.5 to 3.0.
    [Show full text]
  • Slope Stability 101 Basic Concepts and NOT for Final Design Purposes! Slope Stability Analysis Basics
    Slope Stability 101 Basic Concepts and NOT for Final Design Purposes! Slope Stability Analysis Basics Shear Strength of Soils Ability of soil to resist sliding on itself on the slope Angle of Repose definition n1. the maximum angle to the horizontal at which rocks, soil, etc, will remain without sliding Shear Strength Parameters and Soils Info Φ angle of internal friction C cohesion (clays are cohesive and sands are non-cohesive) Θ slope angle γ unit weight of soil Internal Angles of Friction Estimates for our use in example Silty sand Φ = 25 degrees Loose sand Φ = 30 degrees Medium to Dense sand Φ = 35 degrees Rock Riprap Φ = 40 degrees Slope Stability Analysis Basics Explore Site Geology Characterize soil shear strength Construct slope stability model Establish seepage and groundwater conditions Select loading condition Locate critical failure surface Iterate until minimum Factor of Safety (FS) is achieved Rules of Thumb and “Easy” Method of Estimating Slope Stability Geology and Soils Information Needed (from site or soils database) Check appropriate loading conditions (seeps, rapid drawdown, fluctuating water levels, flows) Select values to input for Φ and C Locate water table in slope (critical for evaluation!) 2:1 slopes are typically stable for less than 15 foot heights Note whether or not existing slopes are vegetated and stable Plan for a factor of safety (hazards evaluation) FS between 1.4 and 1.5 is typically adequate for our purposes No Flow Slope Stability Analysis FS = tan Φ / tan Θ Where Φ is the effective
    [Show full text]
  • CE2112: Laboratory Determination of Soil Properties and Soil Classification
    CE2112: Laboratory Determination of Soil Properties and Soil Classification Laboratory Report G1: Index and Consolidation Properties G2 Shear Strength Year 2013/2014 Semester 2 PENG LE A0115443N 1 Table of Contents 1. Executive Summary ................................................................................................................ 4 2. Overview .................................................................................................................................. 5 3. Atterberg Limits Tests ........................................................................................................... 6 3.1. Principles ............................................................................................................................ 6 3.2. Plastic Limit (PL) ............................................................................................................... 7 3.3. Liquid Limit (LL) ............................................................................................................... 8 3.4. Classification of the Soil .................................................................................................... 9 3.5. Discussion......................................................................................................................... 10 4. One Dimension Consolidation Test .................................................................................... 11 4.1. Principles of One Dimension Consolidation Test ...........................................................
    [Show full text]
  • Physics-Ii Content
    CLASS-11th THE CENTRAL BOARD OF SECONDARY EDUCATION PHYSICS-II CONTENT PART - B Unit 7 – Properties of Bulk Matter 1-88 Mechanical Properties of Solids 1 Mechanical Properties of Fluids 25 Thermal Properties of Matter 51 Unit 8 – Thermodynamics 89-113 Laws of Thermodynamics 89 Unit 9 – Behavior of Perfect Gases and Kinetic 114-133 Theory of Gases Kinetic Theory 114 Unit 10 – Oscillations and Waves 134-191 Oscillation 134 Waves 172 Chapter 9 MECHANICAL PROPERTY OF SOLIDS Content V Elasticity And Plasticity V Elastic Behaviour in solids V Stress And Strain V Hooke’s Law V Stress Strain Curve V Elastic moduli (introduction and determination) V Young’s Modulus V Bulk Modulus V Shear Modulus V Poisson's ratio V Application of Elastic Behaviour of Material V Elastic potential energy in a stretched wire V Important Questions. www.toppersnotes.com 1 Elasticity It is the property of a body, to regain its original size and shape when the applied force is removed. The deformation caused as a result of the applied force is called elastic deformation. Plasticity Some substance when applied force gets permanently deformed such materials are known as plastic material and this property is called plasticity. Reason for Elastic behaviour of solids When a solid is deformed, atoms move from its equilibrium position, when the deforming force is the interatomic force pulls the atom back to the equilibrium position hence they regain their shape and size. This can be better understood using the spring and ball structure on the left, where the ball represents the atoms and the force of spring represents the intermolecular force of attraction.
    [Show full text]
  • Stability Charts for a Tall Tunnel in Undrained Clay
    Int. J. of GEOMATE, April, 2016, Vol. 10, No. 2 (Sl. No. 20), pp. 1764-1769 Geotech., Const. Mat. and Env., ISSN: 2186-2982(P), 2186-2990(O), Japan STABILITY CHARTS FOR A TALL TUNNEL IN UNDRAINED CLAY Jim Shiau1, Mathew Sams1 and Jing Chen1 1School of Civil Engineering and Surveying, University of Southern Queensland, Australia ABSTRACT The stability of a plane strain tall rectangular tunnel in undrained clay is investigated in this paper using shear strength reduction technique. The finite difference program FLAC is used to determine the factor of safety for unsupported tall rectangular tunnels. Numerical results are compared with upper and lower bound limit solutions, and the comparison finds a very good agreement with solutions to be within 5% difference. Design charts for tall rectangular tunnels are then presented for a wide range of practical scenarios using dimensionless ratios ~ a similar approach to Taylor’s slope stability chart. A number of typical examples are presented to illustrate the potential usefulness for practicing engineers. Keywords: Stability Analysis, Tall Tunnel, Undrained Clay, Factor of Safety, FLAC, Strength Reduction Method INTRODUCTION C/D and the strength ratio Su/γD. This approach is very similar to the widely used Taylor’s design chart The critical geotechnical aspects for tunnel design for slope stability analysis (Taylor, 1937) [9]. discussed by Peck (1969) in [1] are: stability during construction, ground movements, and the determination of structural forces for the lining design. The focus of this paper is on the design consideration of tunnel stability that was expressed by a stability number initially defined by Broms and Bennermark (1967) [2] in equation 1: = (1) − + Fig.
    [Show full text]
  • Shear Strength Examples.Pdf
    444 Chapter 12: Shear Strength of Soil Example 12.2 Following are the results of four drained direct shear tests on an overconsolidated clay: • Diameter of specimen ϭ 50 mm • Height of specimen ϭ 25 mm Normal Shear force at Residual shear Test force, N failure, Speak force, Sresidual no. (N) (N) (N) 1 150 157.5 44.2 2 250 199.9 56.6 3 350 257.6 102.9 4 550 363.4 144.5 © Cengage Learning 2014 t t Determine the relationships for peak shear strength ( f) and residual shear strength ( r). Solution 50 2 Area of the specimen 1A2 ϭ 1p/42 a b ϭ 0.0019634 m2. Now the following 1000 table can be prepared. Residual S shear peak S force, T ϭ residual ؍ Normal Normal Peak shearT S؅ f r Test force, N stress, force, Speak A Sresidual A no. (N) (kN/m2) (N) (kN/m2) (N) (kN/m2) 1 150 76.4 157.5 80.2 44.2 22.5 2 250 127.3 199.9 101.8 56.6 28.8 3 350 178.3 257.6 131.2 102.9 52.4 4 550 280.1 363.4 185.1 144.5 73.6 © Cengage Learning 2014 t t sЈ The variations of f and r with are plotted in Figure 12.19. From the plots, we find that t 2 ϭ ؉ S؅ Peak strength: f (kN/m ) 40 tan 27 t 2 ϭ S؅ Residual strength: r(kN/m ) tan 14.6 (Note: For all overconsolidated clays, the residual shear strength can be expressed as t ϭ sœ fœ r tan r fœ ϭ where r effective residual friction angle.) Copyright 2012 Cengage Learning.
    [Show full text]